Universally applicable photometer with adapters for reducing the measuring angle

ABSTRACT

The present disclosure relates to a universally applicable light-measuring device, especially photometer, which comprises a main measuring device, e.g. an exposure meter, and easily exchangeable auxiliary measuring devices or adapters for reducing the measuring angle which, when individaully attached to the main measuring device, form therewith new unitary devices, as to outer appearance and function. All adapters have identical bottom portions with two hooklike extensions to be received in corresponding recesses in the main measuring device. One of the extensions is resiliently journaled and may be displaced by a pushbutton for disconnecting the adapter from the main device.

United States Patent [72] inventors Erwin Pfaflenberger;

Germany [211 App]. No. 870,961 [22] Filed July 22, 1969 [45] PatentedNov. 30, 1971 [73] Assignee P. Gossen & Co. GmbH Erlangen, GermanyOriginal application Apr. 19, 1967, Ser. No. 631,947. Divided and thisapplication July 22, 1969, Ser. No. 870,961

[54] UNIVERSALLY APPLICABLE PHOTOMETER WITH ADAPTERS FOR REDUCING THEMEASURING ANGLE 2 Claims, 3 Drawing Figs.

[52] U.S. Cl 356/218, 24/230, 356/222, 356/225 [51] G11ljl/42 I [50]356/218. 222-226, 73; 24/230 AM [56] References Cited UNITED STATESPATENTS 1,990,361 2/1935 Bailey, Jr 356/225 2.175.027 10/1939 McCune....356/224 2,579,661 12/1951 Freund 356/73 Hans Forsterling, both ofErlangen,

OTHER REFERENCES Gossen. P.S.A. Journal. Dec 1966, pp. 10- 11v PrimaryExaminer- Ronald L. Wibert Assistant Examiner-Warren A. SklarAttorney-Nolte and Nolte ABSTRACT: The present disclosure relates to auniversally applicable light-measuring device. especially photometer.which comprises a main measuring device. e.g. an exposure meter. andeasily exchangeable auxiliary measuring devices or adapters for reducingthe measuring angle which. when individaully attached to the mainmeasuring device. form therewith new unitary devices, as to outerappearance and function. All adapters have identical bottom portionswith two hooklike extensions to be received in corresponding recesses inthe main measuring device. One of the extensions is resilientlyjournaled and may be displaced by a pushbutton for disconnecting theadapter from the main device.

PATENTEU nuvao 1911 INVENTORS ERWIN PFAFFENBERGER HANS FOSTERLINGATTORNEYS UNIVERSALLY APPLICABLE PHOTOMETER WITH ADAPTERS FOR REDUCINGTHE MEASURING ANGLE This application is a division of application, Ser.No. 631,947, filed Apr. 19, 1967.

SUMMARY OF THE INVENTION The present invention relates to a universallyapplicable photometer, especially for carrying out phototechnicalmeasurements. It comprises a main measuring device and a plurality ofmeasuring angle adapters, which can be connected to the main or basicdevice by identical means in such a way that a new and unitary device asto appearance and function is created while permitting easy exchange.The main device by itself or in combination with the various adaptersmay be used to carry out a number of different photometric measurements.

In order to solve the problems involved as to appearance and function,it was necessary to design the adapters to be combined with the maindevice so that upon assembly a unitary device is produced. To this endall adapters are provided with the same connecting device or arrangementwhich permits exchange in a very simple manner. The connecting device isnot apparent at the main or basic device since the latter is to be usedalso without the adapters. In addition, care had to be taken that adiffusor which is nondetachably but displaceably connected to the maindevice, is located outside the path of the rays, to be measured duringuse of the adapters, bodily and functionally. Moreover, the individualelements of the combination have to be adapted to the physicalproperties of the main device, which operates as an exposure meter.

It is an object of the present invention to provide a compositelight-measuring device, especially a photometer, which is universallyapplicable for carrying out a large number of photometric measurements.

It is another object of the present invention to provide alight-measuring device as set forth above which comprises a mainmeasuring device and devices which can easily be connected to anddetached from the main measuring device.

Still another object consists in the provision of cooperating means forconnecting the auxiliary measuring devices, one at a time, to the mainmeasuring device.

According to still another object of this invention, novel auxiliarymeasuring devices or adapters are proposed for reducing the measuringangle of an objective.

The present invention is illustrated by way of example in the followingdrawings, in which:

FIG. I is a top view, partly in section, of an exposure meter with anadapter;

FIG. 2 is a cross section of an adapter for reducing the measuring angleof the exposure meter, and taken along the line 2-2 of FIG. 3;

FIG. 3 is a top view of the adapter of FIG. 2.

For connection to the main measuring device 3, all adapters l have anidentical bottom la, lb with a stationary hooklike extension 2 and aresilient movable nose portion adapted respectively to engage recesses4, 7 at the top of the exposure meter. The resilient nose portion 5 maybe depressed by a key 6 accessible from the outside and, therefore,permits a fast exchange. F urthennore, a recess for the above-mentioneddiffusor is provided which, upon attachment of an adapter is displacedin such a way that it occupies a position in this recess.

The connecting device proper, according to FIG. 1, comprises anextension 2 in the form of a hook and arranged at the bottom lb ofhousing 1 of the adapter. Extension 2 slides into a recess 4 at the topof the main device 3 when the adapter is attached to the latter. Aresilient nose 5 with a key 6 adapted to be actuated by hand from theoutside is arranged opposite extension 2. Nose 5 is resiliently held inhousing 1 of the adapter and is caught in a second recess 7 of maindevice 3. In this way, the main device and the adapter are fixedlyconnected to each other. For purposes of disconnecting the adapter fromthe main device, key 6 is depressed whereby the adapter may easily bedetached. Prior to the connection of the adapters to the main device thediffuser 3a is slidably displaced so that it is located below thedepression la of the adapter and is received therein.

The main device 3 proper, i.e., the exposure meter in the embodimentshown, has the customary measuring angle of ap proximately 30, in otherwords, is somewhat smaller than the picture angle of an objective ofnormal focal distance. In order to be able to measure with smallermeasuring angles which correspond to the picture angles of ordinaryteleobjectives, as, for instance, with an angle of 15 or 75 the path ofthe rays has to be reduced to the desired value by means of an adapterand a variable aperture of a diaphragm.

The structure of this adapter for reducing the measuring angle has to besuch that a compact unit and light losses as small as possible areobtained. The optical structure comprises three parts, viz two convex orcollecting lenses 13, 15 and a variable or adjustable diaphragm 16 whichis arranged between the two lenses close to the lens on the exit side.As an optimum solution, the lens 13 on the entrance side is so designedthat it produces an image of the distant objects in the plane of thediaphragm 16. The focal distance f, of this lens and the aperture of thediaphragm with the radius a are so dimensioned that the desiredacceptance angle satisfies the condition:

tanor=a/f The focal distance of the lens 15 on the exit side is soselected that the opening or aperture of the lens on the entrance sideappears on a reduced scale on a photoconductive cell or photoresistanceof the main or basic measuring device. This image is produced, accordingto FIG. 1, with the cooperation of the lens 3b on the entrance side ofthe main device, which receives this image from lens 15 of the installedadapter via conventional light path means, not shown. The variablediaphragm is formed by a slide 16 with two different size diaphragmapertures, one of which appears in the drawing. Furthermore, an opticalviewfinder l0, 12, 14 is incorporated in the housing of the measuringangle reducing adapter, since it is very difficult without this aid tosight the object to be measured accurately when small measuring anglesare involved.

The just-mentioned adapter for reducing the measuring angle. Itcomprises a housing 8 with a viewing opening 9 for the viewfinder, whichis covered by a small glass plate 10. Two annular, colored grooves llrand 11g are ground into this plate and indicate in the viewfinder thelimits of the respective measuring angle in color (red and green). Twolenses l2 and 13 are arranged on that side which faces the object beingmeasured. Lens 12 in combination with a deviating mirror 14 serves asfinder and produces images of distant objects on the small glass plate10, whereas lens 13 and lens 15, in combination with disc diaphragm 16arranged adjacent lens 15, serve as actual measuring angle limitingmeans. Diaphragm 16 has two apertures corresponding to the measuringangles 15 and 75 and is adjustable from the outside by means of a slide16a diagrammatically illustrated in FIGS. 2 and 3. When reading theexposure values on the main device and when adjusting the calculatingring 3g according to FIG. 1, a reading mark 3e or 3 f which is offsetwith regard to the main reading mark 3d is to be used because of thelight loss in view of the reduction of the measuring angle to 15 and 7.5respectively. The symbols corresponding to these marks are also shown onslide and one of them (3e) is visible in the corresponding position ofthe latter (see FIG. 3). It is, of course, to be understood that insteadof the two measuring angles of 15 and 7.5", selected by way of examplealso three or more angles with different values may be accommodated inthe diaphragm 16.

While in some of the Figures of the drawing the adapters have been shownby themselves, it is to be understood that each of them has to beconnected to the main measuring device 3 as shown in FIG. 1 to formtherewith a complete, operable unit.

Although the invention has been described with reference to specificembodiments thereof, it is not intended to limit the invention to suchspecific embodiments alone, but it should be interpreted in the scope ofthe appended claims.

What is claimed is:

l. A light-measuring device especially for phototechnical measurements,comprising main measuring means having a measuring angle at which lightmay enter the main measuring means; auxiliary measuring means having alight entrance side and a light exit side; means on the auxiliarymeasuring means to interconnect it with the main measuring means so asto form a unitary device; and a system in the auxiliary measuring meansfor reducing the measuring angle of said main measuring means, saidsystem comprising a first lens on the light entrance side and a secondlens on the light exit side thereof; a movable diaphragm, said firstlens producing an image of objects being measured, in the plane of saiddiaphragm; a light inlet lens and a photoresistance in said mainmeasuring means,; the focal distance of said second lens being such thatthe latter, in combination with said light inlet lens, produces areduced image of the opening of said first lens on said photoresistance.

2. A light measuring device as claimed in claim 1, which includes: anoptical viewfinder in said auxiliary measuring device, and transparentplate means in said viewfinder with annular colored grooves providedtherein.

* t I! t t

1. A light-measuring device especially for phototechnical measurements,comprising main measuring means having a measuring angle at which lightmay enter the main measuring means; auxiliary measuring means having alight entrance side and a light exit side; means on the auxiliarymeasuring means to interconnect it with the main measuring means so asto form a unitary device; and a system in the auxiliary measuring meansfor reducing the measuring angle of said main measuring means, saidsystem comprising a first lens on the light entrance side and a secondlens on the light exit side thereof; a movable diaphragm, said firstlens producing an image of objects being measured, in the plane of saiddiaphragm; a light inlet lens and a photoresistance in said mainmeasuring means,; the focal distance of said second lens being such thatthe latter, in combination with said light inlet lens, produces areduced image of the opening of said first lens on said photoresistance.2. A light measuring device as claimed in claim 1, which includes: anoptical viewfinder in said auxiliary measuring device, and transparentplate means in said viewfinder with annular colored grooves providedtherein.